[llvm] [LAA] Be more careful when evaluating AddRecs at symbolic max BTC. (PR #128061)

[Florian Hahn via llvm-commits]

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@@ -188,9 +188,91 @@ RuntimeCheckingPtrGroup::RuntimeCheckingPtrGroup(
   Members.push_back(Index);
 }
 
+/// Returns \p A + \p B, if it is guaranteed not to unsigned wrap. Otherwise
+/// return nullptr.
+static const SCEV *addSCEVOverflow(const SCEV *A, const SCEV *B,
+                                   ScalarEvolution &SE) {
+  if (!SE.willNotOverflow(Instruction::Add, false, A, B))
+    return nullptr;
+  return SE.getAddExpr(A, B);
+}
+
+/// Returns \p A * \p B, if it is guaranteed not to unsigned wrap. Otherwise
+/// return nullptr.
+static const SCEV *mulSCEVOverflow(const SCEV *A, const SCEV *B,
+                                   ScalarEvolution &SE) {
+  if (!SE.willNotOverflow(Instruction::Mul, false, A, B))
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fhahn wrote:

Added a comment, thanks. They must have the same type for A * B to be valid.

https://github.com/llvm/llvm-project/pull/128061